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I need help in "transcription" of my logs to get understanding what's going on :)

Brief inro: full stock Celica Gt-Four (st185) with installed AEM Logger and Greddy e-01 boost-controller (it was in boost-off mode during session). I've wired signals from MAF, RPM, water temp, and throttle position sensors to AEM. What I was seeking:

The car has poor acceleration and "jerks" when I actively press a throttle. There are two cases here:

- when I press to WOT or ~50%-70 nothing happens, then the car starts to accelerate slowly, got "jerking" at ~2000-2500 RPM then stabilizes and accelerates normally.

- when I press throttle gently, the car accelerates more or less smoothly

I've got logs, here is a sample of case No 1.

My questions are:

1. Is MAF (as you can know, st185 has VAF-type actually) signal jittered because of jittered RPM (by some unknown reason) or MAF signal actually causes RPM jitter? I can't understand what I see :) (Screenshot_6.png)

2. Why RPM can be so "noisy" at high levels? (Screenshot_6.png)

3. What is this? I can't understand this plateau while RPM is dropping and the throttle is fully closed. (Screenshot_7.png)

Thanks a lot!

Attached Files


Alexander normally when i have seen this it is from retarded ignition timing

my sugestion would be to check the base timing and check the ignition advance is also working correctly.

Regards Ross

Hi Ross!

Good point! I think that is it. I changed a distributor before that and probably set the wrong ignition timing.

Thank you!

Should write for the future internet archeologists :)

I've checked an ignition and it turned out that it was perfectly set by my hand (10 deg to BTDC).

Finally, I added AFR to log and distinctly saw a lean AFR at idle. st185 has a stupid 2-speed fuel pump (controlled by fuel pump relay. It switches voltage from 6v to 12v exact at 2500-3000 RPM. Throwed relay in a bin, set a jumper, and got my smooth boost. Woohoo!